The field of the invention is the field of measurement of topological features on the surface of a substrate, principally but not limited to using focused electron beams and ion beams.
It is an object of the invention to produce a method of determining the topography of a surface of a substrate, particularly where the substrate has no sharp contrasts in material, crystallography, or angle.
It is an object of the invention to produce a method of determining the focusing conditions for an electron or an ion beam to focus the beam on a surface of a substrate, particularly where the substrate has no sharp contrasts in material, crystallography, or angle.
It is an object of the invention to produce a method of determining the depth of features in a generally flat, otherwise featureless surface.
It is an object of the invention to produce a method of determining features of sidewalls of a hole or trench in a substrate, particularly when the sidewall is sloped, vertical or undercut.
A focused particle bean, such as an electron, ion, atom, or molecular bean is directed on to the surface of a substrate. Scattered particles which travel in a straight line from the surface irradiated are collected in a particle detector. A particle blocking material having an edge is interposed between the surface and the particle detector, and the location of the shadow cast by the edge of the material is measured. The relative position of the surface and the edge casting the shadow can then be determined. Sweeping the particle beam can then be used to build up a topographic map of the surface. The depth and the sidewalls of holes and trenches are measured by appropriately changing the angle of incidence of the particle beam.